1. Field of the Invention
The present invention relates to wireless communication systems, such as a wireless LAN (Local Area Network), in which a plurality of wireless stations wirelessly communicate with one another, to wireless communication control apparatuses and methods, to wireless communication apparatuses and methods, and to storage media. More particularly, the present invention relates to a wireless communication system for allocating a transmission channel used by each wireless communication apparatus in each transmission frame defined by a beacon signal transmitted by a coordinator (wireless control station), to a wireless communication control apparatus and method, to a wireless communication apparatus and method, and to a storage medium.
More specifically, the present invention relates to a wireless communication system for allocating a transmission channel in a transmission frame by each wireless communication apparatus making a channel allocation request to the coordinator, to a wireless communication control apparatus and method, to a wireless communication apparatus and method, and to a storage medium. More particularly, the present invention relates to a wireless communication system for allocating a transmission channel in accordance with characteristics of information to be transmitted when a channel allocation request is made, to a wireless communication control apparatus and method, to a wireless communication apparatus and method, and to a storage medium.
2. Description of the Related Art
As the functions of computers have become more sophisticated, multiple computers are interconnected to form a LAN. Accordingly, information such as files and data can be shared, peripheral devices such as printers can be shared, and information can be exchanged by forwarding email and data.
In known LANs, computers are interconnected by wires using optical fibers, coaxial cables, or twisted pair cables. It is necessary to perform construction work to establish a connection in a wired LAN. As a result, LANs cannot be created easily, and cables become bothersome. After a LAN is created, the range in which each apparatus can move is limited by the cable length, which is inconvenient.
Wireless LANs have been attracting public attention as systems for liberating users from known wired LANs. In these wireless LANs, most cables can be omitted in a workspace such as in an office. Terminals such as personal computers (PCs) can be moved in a relatively easy manner.
Currently, the standardization of personal area networks (PAN) has been under consideration to form a small wireless network among a plurality of electronic apparatuses for personal use so that they can communication with one another.
For example, high-speed data transmission exceeding 20 Mbps is to be standardized as the IEEE 802.15.3 standard.
In IEEE 802.15.3, a plurality of wireless communication apparatuses is used to form a wireless personal area network. In order that the wireless communication apparatuses can transmit predetermined information to each another, a transmission channel, that is, a time slot, is dynamically allocated and transmission is performed.
In this type of wireless personal network, one wireless communication apparatus operates as a control station, referred to as a “coordinator”. A personal area network is formed within a range of 10 m from the coordinator.
The coordinator transmits a beacon signal at predetermined intervals, referred to as the beacon period. This beacon period is defined as a transmission frame. The transmission frame may be constant or variable from one frame to another. A time slot to be used by each wireless communication apparatus is allocated in each transmission frame.
As methods for allocating a time slot, for example, the method referred to as a “guaranteed time slot” and the method referred to as “dynamic TDMA (Time Division Multiple Access)” are employed. A predetermined transmission capacity is guaranteed, and a transmission channel is dynamically allocated.
In channel allocation methods assumed in known personal area networks, an available channel to be allocated to each wireless communication apparatus is allowed to change in each transmission frame.
Unless a wireless communication apparatus receives a beacon signal transmitted from the coordinator at the beginning of a transmission frame, the wireless communication apparatus cannot obtain channel allocation information in that transmission frame and thus cannot transmit information.
Even if, for example, the wireless communication apparatus tries to make a channel allocation request by using a guaranteed time slot, the wireless communication apparatus cannot accurately detect the transmission area allocated thereto to transmit information.
In cases in which transmission is to be performed while the transmission capacity remains the same, re-transmission is not to be performed, and broadcast transmission is to be performed, it is clear that only a predetermined transmission area that is determined from the beginning is necessary. When a transmission channel is dynamically changed by applying dynamic TDMA to transmit data in these cases, an unused transmission channel remains, which is wasteful and inefficient.